Originally Posted by
Mike Blue
When I look at the start of the curve, the first thing that comes to mind is that it's not possible to travel backward in time. The time to quench begins on the left most line of the chart, not the right side of the curve. Time moves left to right on this chart.
Are you measuring the Curie temperature? Or are you testing the hot billet to determine it's magnetism? If the billet is non magnetic you're undoubtedly past the Curie point. If so, then focusing on a one-point temperature isn't necessary when you have the state of the metal where you want it before you attempt to harden it.
If you want me to respond to what you've been told, I'd prefer to have a conversation with the fellows that told you. I can respond to what you have personally experienced quenching steels much easier. Have you had trouble quenching to acceptable hardness any of the steels you mention? I can say that in my experience, a TTT diagram can seem to indicate that I can't move fast enough to quench a steel taken from the heat and into a quench medium fast enough (and I grow slower every day.) But, if I don't dawdle from the fire to the quench, the steel seems to harden just fine. I'm trying to simplify the process so beginners can get started and be successful.
Paragraphs don't help me watch what you are doing to know if what you do in your shop is working. Only you can know that given the limits of this media.
And yes, the metallurgists who developed these curves were not heat treating either knife-shaped or razor-shaped cross sections. As a general guide, the TTTT diagrams are helpful. Where the shape of the materials we work in creates a potential for not-knowing or uncertainty...it is up to the smith/maker with their hand on their work to determine how comfortable they are working in an area not defined very well. You have to heat treat a lot of blades and ttake good notes for yourself. Then you'll have learned something the metallurgists can't tell you.